An antenna or the like mounted on an artificial satellite may need to feed high-frequency waves to a deployment structure because of system configuration.
Flexible guided lines such as cables and flexible waveguides have been used as conventional methods. FIG. 1 shows an example in a Patent Literature 1 where a flexible waveguide 4 is used at a deployment part in a deployment structure consisting of a first flat panel 1a and a second flat panel 1b with a spiral spring 2 and a 2-piece hinge 3a and 3b. In general, however, flexible waveguides 4 have larger RF loss than rigid waveguides as the frequency increases, which results in degradation of their RF characteristics. RF losses of flexible waveguides are resistive and may lead to increase in the system noise temperature in a receiver system due to resistive loss. Flexible waveguides have still resistive torque for bending that cannot be ignored and the resistive torque tends to increase at low temperature with some degree of uncertainty. Therefore in some cases flexible waveguides may cause troubles in design and test of deployment mechanism.
In contrast, there have been proposed methods in which the flexible waveguide is not used in the deployment portion in a deployment structure consisting of a first flat panel 1a, a second flat panel 1b, a spiral spring 2 and a 2-piece hinge 5a and 5b as shown in FIGS. 2 and 3. A first method proposes a system in which a rigid waveguide alone is utilized and, for a waveguide opening in the deployment portion, a mechanism utilizing a hinge is used to fit together convex portion A and concave portion B (as shown in FIG. 2) or pin portion P and hole portion H (as shown in FIG. 3) provided in the vicinity of two waveguide openings. This is disclosed in Patent Literature 1. Conceptual illustrations are also shown in FIGS. 2 and 3 of Patent Literature 1. However, the first method has a problem with machine accuracy for fitting or the amount of torque. Insufficient fitting force may cause a high-frequency loss and additional noise due to an increase in contact resistance between conductors. Thus, an example of practice of the system has not been known.
A second method utilizes a rotary joint in which waveguides fixed to two structures, respectively, which rotate about a certain shaft, are high-frequency coupled together, utilizing axisymmetric properties about the rotating shaft. FIG. 4 illustrates an example of a rotary joint using a coaxial cable, and FIG. 5 illustrates an example of a rotary joint using a circular waveguide (Non-Patent Literature 1). The rotary joint of FIG. 4 includes a central conductor on rotor side, an outer conductor on rotor side, a central conductor on stator side, and an outer conductor on stator side as shown in FIG. 4. The rotary joint of FIG. 5 includes a circular waveguide TM01 mode, a rectangular waveguide TE10 mode, and a TA10/TM01 mode converting portion as shown in FIG. 5. In this method, the transmitting TE10 mode of rectangular waveguides is converted to a TM01 mode of circular waveguides or a TEM mode of coaxial lines and RF loss occurs at the mode conversion. Moreover, a hinge shaft which serves as a deployment mechanism for a load or accuracy of position is coaxial with the rotating shaft of the rotary joint which serves for electrical characteristics, which in turn increases complexity of the mechanism. A direction of high-frequency wave feeding is often orthogonal to a deployment shaft; however, a system using the rotary joint requires that a high-frequency waveguide make two right-angle turns, which thus increases the size of the mechanism.